Spectrophotometric analysis is a method of chemical analysis based on the absorption by a particular impurity in a sample under test of light of a specific wavelength. The instruments used for spectrophotometric analysis are known as spectrophotometers, and these instruments are capable, by selecting different wavelengths of light of measuring the percent concentration of various known impurities in the sample. Spectrophotometers are in present-day widespread use for clinical purposes, for testing serum derived from the blood of patients. The Abbott Bichromatic Analyzer (ABA-100) referred to above represents such a clinical spectrophotometer.
A simple spectrophotometer consists of a source of light, a monochromator containing a prism or grating which disperses the light so that only a limited wavelength, or frequency range, is allowed to irradiate the sample or specimen, the sample itself, and a detector, such as a photocell which measures the amount of light transmitted by the sample to provide a reading of the "absorbance" of the sample. The sample is placed in a small cell or "cuvette" as the cell is called, the walls of which are transparent at the wavelength of light being used, and the cuvette is interposed between the surface of light and the photocell.
The ABA-100 is described in U.S. Pat. No. 3,748,044. It is a system for analyzing reactions that take place within a plurality of individual specimens. According to a principal feature of the ABA-100 system, a dispenser is provided that transfers specimens to a disposable cuvette for holding each of the specimens in an individual compartment. Analyzing means are also used to generate and transmit a beam of radiant energy through the specimens. This mode of operation produces an analysis signal having a value proportional to a property of a predetermined specimen each time the beam passes through that specimen.
Each time the beam passes through a specimen, address means generate an identity code that uniquely identifies that specimen. Cycling means are employed for causing the beam to separately pass through each of the specimens during multiple cycles of operation. For example, during a first cycle of operation, a first set of analysis signals having a first set of values corresponding to the specimens may be created. Likewise, during a second cycle of operation, a second set of analysis signals having a second set of values may be created. Memory means for instantaneously storing the values of the analysis signals at addresses corresponding to the predetermined specimens are also utilized. Electronic processing means are used in the ABA-100 system to enable the cycling means and memory means, as well as to compare the values stored in the memory means with additional values created by the analyzing means in order to evaluate the reactions taking place in the specimens.
For example, in order to determine the rate at which relatively slow reactions take place within each of the specimens, the memory means in the ABA-100 system are used to store the first set of values created during a first cycle of operation. Then, while the second cycle of operation is creating the second set of values, processing means compares the values of the first and second sets of values which correspond to the same specimen. In this way, the rates of reaction of all the specimens are determined during the same period of time.
In order to determine the rate at which a rapid reaction takes place within a predetermined specimen in the ABA-100 system, beams of radiant energy are passed through the predetermined specimen at specified short intervals, such as every 15 seconds. This mode of operation results in a set of time-spaced analysis signals that are sequentially stored in the memory means of the ABA-100. The processing means in the ABA-100 then compares the value of each succeeding analysis signal with the value of a previous analysis signal stored in the memory means. In this manner, the rate of the reaction may be accurately determined over short time intervals.
In order to analyze an end point determination by the ABA-100 system, one of the specimens comprises a known concentration of the substance, and other specimens contain unknown concentrations of the substance. The value corresponding to the known concentration is stored in the memory means of the ABA-100 and other values corresponding to the unknown concentrations are compared with the value stored in the memory means by the ABA-100 processing means.
According to another feature of the ABA-100 system, two wavelengths of radiant energy are generated. The first wave length lies substantially in the center of a predetermined band; and the second wavelength is greater than the first wavelength and lies substantially outside the predetermined band. The radiant energy at the two wavelengths is then sequentially transmitted through the specimens along a single path and is compared in the manner described. According to this feature, the transmission of radiant energy is also interrupted periodically in order to establish a reference level. By using the ABA-100 system, the concentration of a predetermined substance is determined instantaneously with a degree of accuracy heretofore unattainable.
The ABA-100 is capable, for example, of providing an analog output representing the optical transmission of each of a plurality of serum specimens at the selected wavelength, depending upon which test is being conducted. The data analyzing system of the invention may provide outputs representative of percent concentration which has a linear relationship with optical density, so that the percent concentration of the particular impurity may be indicated directly by the system.
As mentioned above, the data analyzing system of the invention is intended to operate in conjunction with a clinical chemistry analyzer spectrophotometer such as the ABA-100 system. The data analyzing system of the invention is capable, inter alia, of directing the sequence of operations of the ABA-100 for any particular test, to perform control statistics, of calibrating results of all types of assays made by the ABA-100, and of printing these results directly into reportable units. The system of the invention is capable of making defined calculations for end point assays, rate reactions, EMIT assays, and specific reactions such as T4.
The data analyzing system of the invention automatically flags out-of-limit data. For each test, the operator can set the standard tolerance and normal range, and the system prints error flags if, for example, the result exceeds the entered normal high range value (NRHI); or if the result is lower than the entered normal low range value (NR LOW), or if any of the standards exceed the entered standard tolerance (TOL).
The data analyzing system of the invention is capable of automatically controlling the ABA-100, and it can, for example, trigger the auxiliary dispenser of the ABA-100 automatically at any carousel station. Moreover, the data analyzing system of the invention can direct the sequence of operations, and it can list all test variables for any test as well as carousel load lists. The system can also perform quality control statistics, specifically, for each test run, the control mean, standard deviation, and coefficient of variation can be printed.